While any report such as this is never 100% accurate, it does provide some sort of guide. They would have reviewed the financials of the clubs which in most cases are publicly available, crowd numbers on game days, viewership on TV, memberships, etc to arrive at their calculations. With Broncos having a market cap on the ASX of $94m, then the brand value of $124m, a circa 30% increase would not be unreasonable if you were looking to acquire it.
While we might not like it, the reality is the AFL has a bigger TV deal, attracts more matchday fans (average was about 38k to 20k in 2024), has more club memberships (admittedly the way clubs calculate them differ), and all this and other metrics would lead to AFL clubs having a higher value, especially for the big AFL clubs. Given how the NRL has grown in recent years, the interesting thing would be if there are prior years values to see what movements there have been.